The President's Power to Respond to Attacks by the Houthis
Michael Ramsey
Somewhat lost among other news, the President has apparently directed substantial military action against the Houthi militia in Yemen. Although I have a more limited view of the President's power to conduct hostilities than some scholars (see here), I think this action is within the President's power.
I assume for this analysis that directing hostilities against a non-state actor such as the Houthis constitutes "war" for constitutional purposes, and thus is potentially limited by the Constitution's assignment of the declare-war power to Congress. (I'm not entirely sure this is correct: I took this position in the article linked above but I have come to somewhat doubt it. If this is not correct, then the President's power is not limited by the declare war clause, and is presumably within his commander-in-chief power.)
The declare war clause would (on this assumption) prevent the President from initiating hostilities against the Houthis. But as I understand the facts, the Houthis have been systematically attacking U.S. shipping, including U.S. naval vessels, in the Red Sea for some time. As a result, the situation is properly understood as the Houthis initiating war against the United States, prompting a U.S. response.
It's widely agreed that the President can direct at least some military response to attacks on the United States, including (at least) attacks on U.S. military forces. The more difficult constitutional question is why this is so. (It's true that Madison said so at the Philadelphia Convention, but that doesn't make it right or explain why it is right.) Alexander Hamilton had an explanation that I find persuasive, as I describe in The President's Power to Respond to Attacks. Writing in response to the Tripoli conflict in 1801, Hamilton reasoned as follows: if a foreign power attacks the United States, that action declares war. The President's action in response to that attach is thus taken within the context of an existing war; it does not declare war itself. Hence, a presidential response does not infringe Congress' declare-war power, and is authorized by the President's commander-in-chief power.
Thinking about the declare-war power this way helps resolve the next constitutional question, which is critical in the Houthi situation. Again, it's widely assumed that the President can direct a response to attacks at least to the extent of defending against the attacks. But can the President go further and order the military to take the offensive against the attackers, as it appears the President has done regarding the Houthis? Hamilton's answer was yes (in the analogous situation with Tripoli) because once war is begun by the other side, the declare war clause does not limit the President's ability to respond, and the commander in chief power allows the President to take military action the President thinks is necessary. On that reading of the clauses, the action against the Houthis -- even very substantial counteroffensive action -- is constitutional.